A common problem associated with valve gated hot runner injection molding systems is the leaking of molten plastic that can occur between the valve pin and the manifold plate. There are many different valve runner or bushing designs that have attempted to stop leakage from occurring, examples of which can be seen in U.S. Pat. No. 4,740,151 issued Apr. 26, 1988; U.S. Pat. No. 5,696,793 issued Dec. 9, 1997; and U.S. Pat. No. 5,849,343 issued Dec. 15, 1998; and U.S. Patent Application No. US 2002/0106419 A1 published Aug. 8, 2002.
Existing valve pin bushings tend to have a high thermal mass concentrated around the valve pin and the manifold plate by having a larger disk head arranged to bear against a manifold, which can result in a hot area next to the valve pin prone to leakage in some applications. Thus, there remains a need for valve pin bushing that is less prone to leakage and which is economical to produce and use.